Known free radical curing systems involve high intensity, heat-generating lamps. Free radical systems historically generate heat with a mercury light source. This limits their use with heat sensitive substrates. Further, such systems can require water heat sinks and/or dichroic filters to prevent infrared (IR) radiation from reaching and distorting or discoloring the substrate. Such measures increase the complexity and cost of processing a substrate making the use of such systems undesirable.
Known ultraviolet light (UV) free radical cure technology is inadequate, e.g., having oxygen inhibition, poor flexibility, and poor adhesion of cured coatings. The failings of known technology include inadequate or difficult curing and cure rates and unsatisfactory substrate throughput rates. Further, known technology is unable to properly coat multidimensional, curved or shaped articles. Known methods are also incapable of properly coating objects having dark areas, or areas having limited light exposure.
Known jet printing technology can utilize a mercury vapor 100 Watt (W) per inch (W/in) or other high-intensity heat-generating curing light source.